Anomalies in the overall shape of the eye can cause visual disorders. Hyperopia ("farsightedness") occurs when the front-to-back distance in the eyeball is too small. In such a case, parallel rays originating greater than 20 feet from the eye focus behind the retina. In contrast, when the front-to-back distance of eyeball is too large, myopia ("nearsightedness") occurs and the focus of parallel rays entering the eye occurs in front of the retina. Astigmatism is a condition which occurs when the parallel rays of light do not come to a single point within the eye, but rather have a variable focus due to the fact that the cornea is aspherical and refracts light in a different meridian at different distances. Some degree of astigmatism is normal, but where it is too high, it must often be corrected.
Hyperopia, myopia, and astigmatism are usually corrected by glasses or contact lenses. Surgical methods for the correction of such disorders are known. Such methods include radial keratotomy (see, e.g., U.S. Pat. Nos. 4,815,463 and 4,688,570) and laser corneal Ablation (see, e.g., U.S. Pat. No. 4,941,093). Further methods include the implantation of polymethylmethacrylate (PMMA) rings, allograft corneal tissue, and hydrogels is well documented. U.S. Pat. No. 4,452,235, to Reynolds, for example, describes a method and apparatus for corneal curvature adjustment involving the implantation of polymeric rings in the eye's corneal stroma to change the curvature of the cornea.
Vacuum devices useful for such ocular surgical procedures are common. For instance, U.S. Pat. No. 4,423,728, to Lieberman, shows a cam-guided trephine for selectively cutting a circular or V-shaped groove about the cornea. The device utilizes a pair of suction rings which affix the apparatus onto the sclera of the patients eye. The vacuum is usually less than about 10 cm of water thereby avoiding raising the intraocular pressure above the physiological levels. The suction ring lies in the anatomically constant area just outside the limbus.
Similarly, U.S. Pat. No. 4,997,437 to Grieshaber, shows a process and apparatus for cornea grinding. The device has a base member which is held to the conjunctiva of the eye by a vacuum space formed about the periphery of the cornea. A rotary grinder is attached to the base member and slides onto the eye through the interior bore of the base member.
Also, U.S. Pat. No 4,662,370, to Hoffmann et al., shows an apparatus for performing lamellar refractive cornea surgery. The device has a base adapted for placement on the sclera of the eye with an annular recess forming a vacuum space for holding the device to the eye while pressing the cornea against an insert of a predetermined shape. The applanate surface of the insert dictates the shape of the corneal lamella cut by a knife riding on a support mounted on the base.
Similarly, U.S. Pat. No. 5,496,339, to Korpnick, shows an apparatus for making a shaped cut of the cornea in the correct position in order to make the refractive change desired. The device has a base with a suction ring adapted to be positioned and held against the sclera of the eye with a corrected surface portion of an insert drawn to the cornea of the eye by the vacuum applied. A knife mounted to a drive device cuts corneal tissue only directly underneath the surface portion.
U.S. Pat. No. 5,011,498, to Krumeich et al., shows a cutting apparatus for excision of a round corneal disk. One embodiment of the invention is installed on an eye vacuum ring having an inner surface that is conformed to the outer surface of the eye. A vacuum draws the eye conforming surface to the outer surface of the eye.
U.S. Pat. No. 5,108,412 to Krumeich et al., shows a suction ring for surgical operations on the eye. The ring has an outer right-angle section and an inner annular ring member carried by the outer section. The inner annular ring has a generally right-angle triangular cross-section. The inner ring possesses an eye-conforming surface and a plurality of segments on its two remaining exterior surfaces. This configuration provides a vacuum space between the two exterior surfaces of the inner ring and the interior of the outer right-angle section. A vacuum draws the eye conforming surface to the outer surface of the eye.
None of these publications provide for a rotationally and translationally stable base member having an improved fit with the surrounding tissue of the eye.
U.S. Pat. No. 5,021,057, to Byrne, Jr., shows an instrument to be used during ocular surgery for the rapid closure of the eye to prevent expulsive choroidal hemorrhaging resulting from operative complications. The device is dome-shaped so to form a seal with the eye to stop expulsive flow. It requires a close fit to the curvature of the anterior ocular surface including the limbus of the eye in order to form a seal. The device has an offset opening allowing a doctor to place sutures in the eye. The location of the opening can be changed by rotating the device by its attached handle. No provision is made for a vacuum space, an open region leaving the cornea substantially exposed or for preventing rotation about the eye.
U.S. Pat. No. 5,063,942, U.S. Pat. No. 5,318,044, U.S. Pat. No. 5,368,604 and U.S. Pat. No. 5,395,385, to Kilmer et al., disclose a device and for re-profiling a cornea. The device may rest on a resilient vacuum ring which is adapted to sit on the sclera of the eye and surrounding the cornea which is to be re-profiled. The top side of the vacuum ring has a number of positioning pins which allow it to be connected to the remainder of the profiling apparatus. No provisions are made in these publications for a discrete, substantially stable vacuum interface region or for preventing rotation of the vacuum ring.
U.S. Pat. No. Des. 370,257, to Christopher, shows an ocular solution applicator having a cup shape and a flat, ovaloid footprint. No provisions are made for a vacuum space an interface with the eye, access to the cornea of the eye, a low-profile application of the curved outer surface to accommodate potentially impinging eyelid tissue or a saddle-shaped periphery.
U.S. Pat. No. 4,026,591, to Cleaveland, shows a contact lens handling tool for placing contact lenses upon the eye or alternately removing them. The publication shows a device having an ovalized an outer cup adapted to bottom in the outer peripheral portion of the eye socket of the user, serving to hold the eyelids back so one of a number of cup-shaped attachments that has clearance to deliver or retrieve a contact lens. Each of the inner cups is shaped to create an appropriate interface with contact lenses. The inner cups will not come into contact with a user's eyelids. The outer cup is not configured to fit into the eye. No provisions are made for a vacuum interface with the eye, access to the cornea of the eye or for preventing rotation of the base member.
One optional aspect of the invention is the use of contact surfaces or vanes which engage the front of the eye to prevent rotation of the inventive device during use.
U.S. Pat. No. 4,429,696, to Hanna, shows a surgical apparatus for precisely cutting out the cornea of the eye by making at least one circular incision. The device is held to the front of the eye by a series of claws, which optionally may be retractable, and suction placed on the central portion of the eye during the cutting operation. There is no suggestion of using the claws in cooperation with a vacuum space.
U.S. Pat. No. 4,417,579, to Soloview et al., shows a surgical device for marking out the cornea in ophthalmosurgial operations utilizing a multiplicity of plates so formed to cause elastic non-destructive deformation of the cornea upon application of force. There is no suggestion of using these plates to prevent rotation or to use them in cooperation with a vacuum space.
U.S. Pat No. 5,403,335, to Loomas et al. discloses a surgical apparatus for producing a generally circular, interlamellar pathway within the cornea. The device is comprised of three major components including a vacuum centering guide having an annular vacuum chamber and a multiplicity of vanes to prevent rotation. There is no suggestion of providing the vacuum centering guide with a sloped or flared edge or an ovalized outer boundary allowing for less interference with impinging eyelid tissue.
The invention described herein is an corneal vacuum centering device. It may serve as an independent apparatus or as a suction ring component which detachably adheres to the front of the eye for guiding and precisely positioning surgical instruments relative to the eye.